diff --git a/ChangeLog b/ChangeLog
index dcb5c56f15..b937b5fd65 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Tue Oct  4 05:53:11 2016  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* regexec.c (OPCODE_EXEC_HOOK): op is p-1 because p is already
+	  incremented.
+
+	* regexec.c (OPCODE_EXEC_HOOK): use the exact end address.
+
+	* regexec.c (match_at): don't call OPCODE_EXEC_HOOK in CASE()
+	  when it comes from goto fail.
+
 Mon Oct  3 21:24:41 2016  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* NEWS: mention Readline.quoting_detection_proc{,=}.
diff --git a/regexec.c b/regexec.c
index 480017ae54..f8813875dc 100644
--- a/regexec.c
+++ b/regexec.c
@@ -1613,12 +1613,13 @@ match_at(regex_t* reg, const UChar* str, const UChar* end,
 #ifdef ONIG_DEBUG_MATCH
 #define OPCODE_EXEC_HOOK                                                \
     if (s) {                                                            \
-      UChar *q, *bp, buf[50];                                           \
+      UChar *op, *q, *bp, buf[50];                                      \
       int len;                                                          \
-      fprintf(stderr, "%4"PRIdPTR"> \"", (*p == OP_FINISH) ? (ptrdiff_t )-1 : s - str); \
+      op = p - 1;                                                       \
+      fprintf(stderr, "%4"PRIdPTR"> \"", (*op == OP_FINISH) ? (ptrdiff_t )-1 : s - str); \
       bp = buf;                                                         \
       q = s;                                                            \
-      if (*p != OP_FINISH) {    /* s may not be a valid pointer if OP_FINISH. */ \
+      if (*op != OP_FINISH) {    /* s may not be a valid pointer if OP_FINISH. */ \
 	for (i = 0; i < 7 && q < end; i++) {                            \
 	  len = enclen(encode, q, end);                                  \
 	  while (len-- > 0) *bp++ = *q++;                               \
@@ -1629,8 +1630,8 @@ match_at(regex_t* reg, const UChar* str, const UChar* end,
       *bp = 0;                                                          \
       fputs((char* )buf, stderr);                                       \
       for (i = 0; i < 20 - (bp - buf); i++) fputc(' ', stderr);         \
-      fprintf(stderr, "%4"PRIdPTR":", (p == FinishCode) ? (ptrdiff_t )-1 : p - reg->p); \
-      onig_print_compiled_byte_code(stderr, p, p + strlen((char *)p),NULL, encode); \
+      fprintf(stderr, "%4"PRIdPTR":", (op == FinishCode) ? (ptrdiff_t )-1 : op - reg->p); \
+      onig_print_compiled_byte_code(stderr, op, reg->p+reg->used, NULL, encode); \
       fprintf(stderr, "\n");                                            \
     }
 #else
@@ -3064,10 +3065,13 @@ match_at(regex_t* reg, const UChar* str, const UChar* end,
       goto finish;
       NEXT;
 
-    fail:
-      MOP_OUT;
-      /* fall */
-    CASE(OP_FAIL)  MOP_IN(OP_FAIL);
+    CASE(OP_FAIL)
+      if (0) {
+        /* fall */
+      fail:
+        MOP_OUT;
+      }
+      MOP_IN(OP_FAIL);
       STACK_POP;
       p     = stk->u.state.pcode;
       s     = stk->u.state.pstr;